Golf ball manufacturers have been able to vary a wide range of playing characteristics, such as compression, velocity, and spin, by altering the composition of the golf ball. Depending on the layer and desired performance, golf ball layers may be constructed with a number of polymeric compositions and blends, including polybutadiene rubber, polyurethanes, polyamines, and ethylene-based ionomers. For example, thermoset polymers, in particular, are used extensively by golf ball manufacturers to form centers and intermediate layers with high resiliency. The resiliency of these thermoset layers is improved by the addition of a coagent prior to curing, usually in combination with a peroxide initiator.
More recently, ionomers and highly-neutralized polymers have been found to be suitable materials for golf ball layers. The ionomers provide relatively hard inner covers having a high flexural modulus and good resiliency which allows the balls to reach a high speed when struck by a club and travel greater distances. By increasing the amount of neutralization of the acid groups, ionomers become stiffer and offer better properties. However, the processability of thermoplastic ionomers is problematic as the percent of neutralization of the acid group increases. For example, as the percent of neutralization increases, the melt flow of the ionomer becomes too low and the ease of processability decreases. As such, the use of currently available thermoplastic ionomers is limited with respect to golf ball layers.
Accordingly, there remains a need for ionomer compositions that are neutralized at high percentages, but in a manner that still allows the use of the resultant polymer compositions in golf ball layers. Advantageously, the compositions of the present invention provide golf ball layers having enhanced resiliency, durability, and compression.